Studies have continued on the effectivess of the anti-protease pepstatin as an "ascites retardant". The studies have been expanded to include observations on the action of pepstatin on different murine tumors to observe if pepstatin is as effective in reducing ascites fluid on these tumors as it is on the previously studied L-1210 and P-185Y tumors. The results (carried out as collaborative effort with the National Cancer Center Laboratories in Tokyo, Japan) demonstrated that pepstatin is effective against a wide variety of tumor strains. Studies have also continued on the purification from human ascites fluid and murine ascites fluid of leukokininogen, the precursor protein of the permeability agent, leukokinin. Our laboratory has purified human leukokininogen to homogeneity and demonstrated that it is a unique protein and not related immunologically to bradykininogen, the precursor of bradykinin. Studies on the purification of murine leukokininogen are in progress. Studies have been carried out on levels of cathepsin D in various organs following administration of pepstatin to mice. The results show clearly that the organ activity of cathepsin D is lowered following pepstatin administration. This is important as another piece of evidence demonstrating that cathepsin D is involved in the formation of ascitic fluid.